<td> width using javascript

Hi all,
I want to access the width of the table data <td> using javascript.
I have code
--------------------------------------------------------------
<table>
<tr>
<td id="widthA" width="20">Width of this cell is to be calculated</td>
</tr>
</table>
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I tried with document.all.widthA.clientWidth and it worked well in IE but in Netscape it is not working.
How can I make it work in both versions???